This invention relates generally to gas injection valves of gas-fired engines or gas engines and more particularly to a gas injection valve of high safety characteristic in which, even in the event of sticking of a needle valve thereof, the passage through which the fuel gas flows to the injection nozzle is positively shut in accordance with the cyclic operation of the engine.
In the prior art, gas injection valves of various constructions for gas engines have been proposed, and many have been reduced to practice. A specific example is the gas injection valve described and illustrated on page 1202 and FIG. 9, Conference Papers of 15th International Congress on Combustion Engines in Paris, 1983. In this gas injection valve, as will be described more fully hereinafter, a single needle valve is provided for closing and opening the flow path of the fuel gas through a gas passage to an injection nozzle. This needle valve is opened by hydraulic pressure and closed by the force of a compression spring.
In the case of defective operation such as jamming or sticking of the needle valve caused by foreign matter caught between the valve and its valve seat or by deformation or breakage of one or more related parts, the gas flow path from the gas passage to the injection nozzle cannot be closed by the needle valve and is kept opened even when it should be closed in the engine working cycle. Consequently, the injection fuel gas at a high pressure is continuously injected into the combustion chamber. This defective operational state could give rise to a dangerous result such as abnormal combustion or continuous flow of fuel gas in the uncombusted state into the engine exhaust pipe or air intake pipe and causing an explosion. This dangerous result could also be caused by damage or breakage of the above mentioned compression spring.